Limits for the 2K pool

Queries using large I/O during sequential scans may still need to perform 2K I/O:

If the 2K pool has its asynchronous prefetch limit set to 0, the first 7 reads are performed by normal asynchronous I/O, and the query sleeps on each read if the pages are not in cache. Set the limits on the 2K pool high enough that it does not slow prefetching performance.